Circular  No.  1  1  t . 

United  States 

BURK, 


griculture, 


L.  O.    HOWARD,    hntomologUt  and  Chief  of  Bureau. 


PREPARATIONS    FOB   WINTER    FUMIGATION     FOB    THE 
<  II  K  I  s   WHITE    I  IV. 

By  A    \\     Mnuun  i  and  \\     W     Yoni 

i\  I  i:«>i>i  i  i  k.n. 

A-  :i  result  of  investigations  conducted  by  the  Bureau  of  Ento- 
mology during  t  In*  past  three  years,  fumigation  for  the  citrus  white 
fly  lias  been  placed  upon  a  practical  basis,  and  the  process  has  been 
M'  simplified  that  any  citrus  grower  can  undertake  the  treatment  of 
hi.s  grove  without  depending  upon  experienced  fumigatora  to  con- 
duct the  operations.  Under  present  conditions  fumigation  is  the 
most  satisfactory  and  profitable  method  of  controlling  the  white  fly 
in  hundreds  of  infested  groves  in  the  ( rulf  coast  cit  rus-groin  ing  regions, 
and  its  usefulness  will  be  extended  i<>  nearly  all  infested  groves 
when  the  practical  recommendations  in  a  forthcoming  bulletin  on 
the  white  fly  have  been  put  into  effect.  The  superior  quality  of 
Florida  citrus  fruits  when  grown  in  groves  free  from  injury  from 
insect  pests  and  the  awakening  of  progressive  growers  to  the  neces- 
sity for  organizations  for  combating  insect  pests  and  for  marketing 
the  fruit  point  to  the  general  adoption  of  the  control  measures  to 
be  recommended  in  the  publication  referred  to. 

At  the  present  time  the  authors  would  recommend  fumigation  for 
the  white  fly  under  the  following  circumstances :  In  groves  isolated 
by  a  distance  of  at  least  200  yards"  from  all  other  infested  grovi 
in  citrus  groves  or  in  citrus-growing  sections  where  the  white  fly  has 
recently  appeared  and  is  still  of  limited  distribution,  and  in  sections 
where  cooperation  can  he  secured  among  growers  in  naturally  isolated 
groups.  In  many  cases  the  owner  of  an  extensive  and  valuable 
grove  which  i-  isolated  except  for  a  small  groveof  a  few  acres  from 
other  infested  groves  can  well  afford  to  loan  his  equipment,  or.  if 
necessary,  fumigate  the  neighboring  grot  e  entirely  at  his  own  expei 


"  Exivri'  t  has  shown  that  a.-  .1  rule  in  i 

fumigation  can  be  practiced  without  it.-'  bung  rendj 

migration  of  adulte.  I *• 

Cir.  111—09 


if  much  lea  extent 


'       -»  -w** 


EPOSITORY 


rather  than  to  permit  the  presence  of  such  grove  to  interfere  with 
his  results. 

Full  directions  concerning  equipment,  chemicals,  and  methods  of 
procedure  in  fumigating  for  t he  citrus  white  fly  have  been  published 
in  a  bulletin  of  this  Bureau."  This  bulletin  is  based  upon  results 
obtained  in  January  and  February,  1907.  Extensive  field  experi- 
ments have  been  conducted  during  the  last  two  seasons  and  the 
additional  results  obtained  will  be  embodied  in  a  supplementary 
report  now  in  preparation  by  the  authors  of  this  circular.  It  is 
hoped  that  before  the  beginning  of  the  next  fumigating  season, 
extending  from  December  1  to  March  1,  a  publication  in  the  Farmers' 
Bulletin  series  of  this  Department  will  be  available.  This  bulletin 
will  contain  only  such  advice  and  directions  as  are  of  practical 
importance  in  fumigation  work  against  the  white  fly,  omitting  the 
details  of  experiments  published  elsewhere  as  the  necessary  basis 
for  establishing  practical  conclusions.  The  present  circular  aims  to 
call  attention  to  the  desirability  and  in  most  cases  necessity  for 
early  preparations  where  fumigation  work  is  planned  for  the  coming 
winter  season;  also  to  give  full  directions  for  such  preparations. 

EQUIPMENT. 

TENTS. 

Orders  for  tents  should  be  placed  as  soon  as  possible  after  it  is 
decided  to  fumigate  a  grove.  Tent  makers  do  not  always  have  on 
hand  a  sufficient  quantity  of  desirable  grades  of  canvas  to  iill  large 
orders.  Delays  in  filling  the  order  may  necessitate  shipment  by 
express,  at  a  cost  several  times  the  expense  of  shipment  by  freight. 

The  first  step  is  the  determining  of  the  sizes  of  tents  required.  It 
is  a  more  common  mistake  to  underestimate  the  size  of  a  tent  required 
than  to  overestimate  it.  Some  allowance  should  be  made  for  the 
growth  of  trees,  in  consideration  of  the  future  use  of  the  tents.  If 
the  trees  are  nearly  uniform  in  size,  the  largest  trees  should  be  selected 
for  measuring.  A  tape  measure  attached  to  a  reel  is  used  in  meas- 
uring trees  to  determine  the  size  of  tent  required.  Standing  a  few 
feet  from  the  outside  branches  of  the  tree  to  be  measured,  enough 
of  the  tape  is  unreeled  to  extend  over  the  to])  of  the  tree  and  about 
half  way  to  the  ground  on  the  other  side,  the  free  end  of  the  tape  is 
held  in  one  hand  and  the  reel  is  thrown  over  the  center  of  the  tree 
and  unreels  the  tape  by  its  own  weight  until  it  reaches  the  ground. 
Two  or  three  attempts  may  be  necessary  in  order  to  have  the  tape 
pass  over  the  center  of  the  tree.  It  should  be  borne  in  mind  that  the 
weight  of  the  tent  will  reduce  the  extreme  height  of  the  tree  and  that 

"  Bui.  76,  Bur.  Ent.,  U.  S.  Dept.  Agr.,   Fumigation  for  the  Citrus  White  Fly  as 
adapted  to  Florida  conditions.     By  A.  W.  Morrill. 
[Cir.  Ill] 


3 


it  i-  therefore  unnecessary  for  the  tape  to  pass  over  the  highest  twigs. 
For  large  trees  6  to  8  feel  should  !»•  added  to  the  number  of  feel  ovei 
the  top  of  the  tree,  as  shown  bj  the  measurement,  and  for  small  trees 
(  to  •'»  feel  ^1 1< mill  !>«•  added.  In  general,  trees  from  10  t"  15  feel 
high  require  tents  between  32  and  14  feel  in  size  .  trees  from  16  to  20 
feel  high  require  tents  II  to  ">s  feel  in  size;  trees  21  to  25  feel  IhltIi 
require  tents  60  to  70  feel  in  size;  and  trees  25  to  30  feel  high  require 
tent-,  70  t'>  76  feel  in  size. 

In  regard  to  the  number  of  tents  required,  it  is  Baie  to  estimate 
thai  with  one  tenl  for  each  I  * ><  >  trees  the  work  of  fumigation  could 
be  completed  in  ten  to  four- 
teen niL_rlil-'  work.  <  me  cicw 
can  handle  from  twentj  to 
twenty-five  small  tents,  l"> 
feet  iii  size  and  smaller,  and 
from  i  •  fifteen  tents,  50 

feet  in  size  and  larger.  Much 
depends  upon  t  he  t  rees  being 
bo  spaced  as  to  obviate  inter- 
ference v>  ith  the w oik  of  shifl - 
ing  the  tent-. 

1  la\  ing  decided  upon  the 
number  and  sizes  of  tents 
required,  orders  should  be 
placed  as  soon  as  possible. 
Samples,  if  8-ounce  army  duck 
.should  be  obtained  from  tent 
and  aw ning  makers  w  ho  arc 
in  a  position  to  furnish  the 

tents.  The  selection  of  1  .'lit 
material  is  a  matter  of  greai 
importance.  Samples  of  duck 
can  be  classified  roughly   in 

regard  to  tightness  by  the  general    texture   and    b)    the  degr< f 

imperviousness  to  direel  rays  of  lighl  when  held  between  the  eye  and 
the  sun,  or  any  bright  light.  Neither  of  these  methods  is  entirely 
satisfactory,  however,  in  selecting  material  for  fumigating  tents. 
With  a  simple  arrangement  devised  by  the  authors  for  testing  the 
tightness  of  material  submitted  to  the  laboratory  at  ( Orlando,  Fla.,  for 
examination,  it  has  been  found  that  samples  of  duck  vary  nearly  50 
percent  in  t  heir  comparative  tightness. 

Figure  1  illustrates  two  extreme  samples  of  8-ounce  duck  which 
differ  to  the  extent  of  17  per  cent  in  this  respect.     As  a  result  of 

"The  size  of  tents  is  expressed  in  terms  of  the  <1i-i.uk  •■  between  parallel  m 
the  octagonal  sheet  of  canvas  of  which  the  tenl  i-  compos 

[Clr.  Ill] 


>  -4*A> 


V'ig.  1.— A?\  undesirable 
ton  durk  for  fui 


the  examinations  made  so  far,  the  authors  strongly  advise  against 
the  use  of  drills  of  any  kind.  The  appearance  of  these  is  much  more 
misleading  than  that  of  ducks,  and  it  seems  impossible  to  estimate 
their  comparative  tightness  except  by  tests  with  special  apparatus. 
Our  experience  up  to  the  present  time  leads  us  to  recommend  closely 
woven  duck  weighing  8  ounces  per  yard,  when  28£  or  29  inches  wide, 
or  about  10  ounces  per  yard  when  the  material  is  36  inches  wide. 
The  more  expensive  grades  of  cloth  are  not  always  the  most  nearly 
gastight.  In  the  case  of  two  leading  concerns  which  have  supplied 
huge  orders  of  tents  for  use  in  Florida,  the  medium  grades  of  mate- 
rial, as  shown  by  the  prices  quoted,  have  been  found  to  be  superior 
in  gas-holding  qualities  to  either  the  cheapest  or  the  most  expensive 
of  the  three  grades  upon  which  prices  were  quoted. 

The  form  of  cover  which  is  at  present  almost  exclusively  employed 
is  the  flat  octagon.  Frequently  those  who  have  never  seen  a  tent  of 
this  kind  fail  to  realize  its  simplicity.  A  square  piece  of  canvas 
woidd  answer  the  purpose  as  well  as  the  octagon,  but  to  save  material 
and  the  handling  of  extra  cloth  the  corners  of  the  square  are  left  off. 
A  perfectly  circular  cover  would  be  more  economical  in  respect  to  the 
amount  of  cloth  required,  but  the  saving  would  not  cover  the  extra 
expense  of  construction  in  this  form. 

For  specifications  tentmakers  may  be  referred  to  Bulletin  76  of 
this  bureau.0  In  general  these  specifications  are  simply  that  the 
form  is  approximately  octagonal,  of  any  desired  size,  made  of  par- 
allel strips  of  goods  overlapped  three-eighths  or  one-half  inch, 
double  stitched,  and  all  raw  edges  hemmed.  In  the  case  of  tents 
50  feet  or  more  in  size  a  reinforcement  is  desirable  across  the  middle 
section  near  each  end,  as  described  in  the  bulletin  referred  to.  It  is 
desirable  that  allowances  be  made  for  shrinkage,  otherwise  a  tent 
after  becoming  wet  and  later  drying  may  not  be  sufficiently  large  to 
cover  trees  of  the  size  for  which  it  was  intended.  The  following 
published  statement  by  the  senior  author  is  of  importance  in  this 
connection  and  is  quoted  in  full:6 

Shrinkage  of  the  goods  after  being  thoroughly  wet  is  an  important  consideration  in 
the  economical  construction  of  fumigating  tents.  In  order  that  the  tents  approxi- 
mate a  regular  octagon,  after  having  been  used  for  fumigating  purposes,  it  is  necessary 
either  to  have  the  goods  thoroughly  shrunk  before  cutting  or  to  make  allowance  for 
subsequent  shrinkage  by  cutting  the  strips  longer.  A  test  made  with  a  brand  of 
8-ounce  duck  commonly  used  in  California  for  fumigating  tents  showed  that  the  shrink- 
age lengthwise  of  the  goods  amounted  to  7.5  per  cent  and  crosswise  0.9  per  cent. 
This  means  that  in  a  50-foot  tent  the  shrinkage  would  result  in  the  full-length  strips 
shortening  3J  feet,  while  the  tent  would  shrink  less  than  0  inches  crosswise  of  the  si  ripe. 
Such  irregularities  might  be  remedied  by  a  skirt  of  6i-ounce  drill,  but  it  is  simpler  to 

a  For  sale  by  the  Superintendent  of  Documents.  Government  Printing  Office, 
Washington,  1>.  ('.     Price.  L5 cents. 

b  l?ul.  76,  Bur.  Ent.,  U.  S.  Dept.  Agr.,  pp.  17-18. 
[Cir.  Ill] 


plan  to  have  each  atrip  cul  longer  bj  a  given  amount  t"r  each  I  per  ■  enl  of  differ 
in  the  length  wi  o  and  i  i                                  In  the  i  i-'-  referred  to  ,il".\>-  this  differ- 
ence i-  6  B  i"-r  cent,  and  each  i"-r  cent  repn  u  tual  differen i  0  ini  hi        \ 

t  i.  hi  constructed  in  thii  manner  would  therefore  measure  before  -linn! 
feel  i  i'1  feel  10J  in  ■  feel   i  in<  he*    lengthwi  •■  •■:  'in-  rtrips  through  the 

middle  section,  an. I  19  feel  n>[.  inches  cro  'in-  strips      \n.r  shrinking,  the 

dimensions  would  !"■  approximately    19  feel   I]  inches  in  each  direction 

On  account  of  the  variation  in  the  shrinkage  of  different  brands  '>f 
duck  it  i>  necessary  to  test  the  crosswise  and  lengthwise  shrinkage  in 
the  Bample  selected.  This  may  be  done  by  marking,  with  a  lead 
pencil,  lines  l  foot  or  more  in  length,  l>'>tli  crosswise  and  length- 
wise of  the  strip  of  goods.  The  Bample  should  be  shrunken  twice, 
each  time  wetting  by  submerging  in  water  for  two  or  three  hours 
and  drying  in  the  sun.  The  amount  of  tin-  shrinkage  can  then  be 
determined  by  measuring  the  pencil  lines  just  referred  to. 

The  marking  of  the  tents  with  graduated  stripes,  which  is  a  part 
of  the  process  of  determining  dosage  requirements  originated  by  the 
senior  author,"  requires  less  than  an  hour  for  each  tent.  The  neces- 
sary preparations  for  this,  therefore,  consist  in  procuring  suitable 
paint  and  arranging  for  a  patch  of  open  Geld  where  the  tents  may  be 
spread  Hat  to  become  saturated  with  rain  or  dew,  thus  producing  the 
desired  shrinkage.  The  importance  of  the  tents  being  thoroughly 
shrunken  before  the  measuring  for  the  graduations  is  obvious. 

Directions  for  "mildew-proofing"  the  tents  will  be  given  in  publi- 
cations now  in  preparation  and  it  is  not  necessary  to  include  them 
in  this  connection,  'rents  should  be  thoroughly  dried  in  the  Bun 
before  being  folded  for  Btorage,  and  in  preparing  them  for  Geld  n-e 
they  should  not  be  exposed  to  rain--  or  dews  any  more  than  is  neces- 
sary to  shrink  as  advised  above. 

POl  I  -    am>   DBRRli  k- 

In  the  Gulf  States,  seasoned  cypress  is  probably  the  besl  material 
available  for  the  manufacture  of  poles  and  derricks  used  in  shifting 
tents.  These  serve  practically  the  same  purpose,  the  former  being 
used  in  handling  tents  up  to  50  feel  in  size  and  the  latter  in  handling 
tents  50  feet  in  size  and  larger.  The  po|i>>  have  no  other  attach- 
ment than  a  rope,  while  t he  derricks  each  consist  of  a  pole  with  a 
crosspiece  and  braces  at  the  base  and  eye-bolt  attachment  for  pulley 
and  tackle  at  the  small  end.  These  poles  and  derricks  can  he  pre- 
pared for  use  in  a  shoii  time,  but  it  is  verj  important  that  the  pole- 
he  cut  and  peeled  h >iilc  enough  before  they  are  n led  for  use  to 

permit  them  to  become  well  seasoned.  Pole-  should  he  carefully 
-elected  in  order  to  have  them  as  straight  and  free  from  knot-  as 
possible.  While  only  two  poles  or  two  derricks  are  needed  for  n-e 
at  one  time,  an  extra  supply  of  both  should  always  he  in  readiness, 

1        cit.,  ] 
(C'ir.  HI] 


so  that  in  case  of  breakage  the  work  can  be  continued  with 
little  interruption.  The  length  of  the  shifting  poles  should  be 
about  2  feet  more  than  the  height  of  the  average  trees,  and  the  small 
end  should  be  about  1\  inches  in  diameter.  The  pples  for  derricks 
should  be  about  3  or  4  feet  more  in  length  than  the  height  of  the 
average  tree,  and  when  ready  for  use  should  be  between  3  and  4 
inches  in  diameter  at  the  base  and  between  2  and  3  inches  in  diam- 
eter at  the  toj).  The  method  of  attaching  the  crosspieces  and  braces 
is  described  and  illustrated  in  Bulletin  76  of  this  Bureau.  If  ordinary 
three-eighths  or  one-half  inch  bolts  are  at  hand,  a  pair  of  derricks  can 
be  prepared  for  use  in  less  than  half  an  hour,  and  this  need  not  there- 
fore be  considered  a  necessary  part  of  the  early  perparations  for 
fumigation.  Cypress  poles  should  be  seasoned  in  a  barn  or  packing 
house,  or  if  out  of  doors  they  should  be  in  the  shade.  Straight  poles, 
while  being  seasoned,  should  be  so  supported  as  to  prevent  bending 
or  warping.  If,  after  cutting,  a  pole  is  found  to  be  crooked,  it  may 
perhaps  be  made  practically  straight  by  the  proper  arrangement  of 
the  supports  when  seasoning. 


GENERATORS    OR    CROCKS. 


In  generating  the  gas  earthenware  crocks  are  used.  In  general, 
trees  5  to  8  feet  high  will  require  crocks  of  li  gallons  capacity;  trees 
0  to  12  feet  high,  crocks  of  2  gallons  capacity;  trees  13  to  16  feet  high, 
crocks  of  4  gallons  capacity;  trees  17  to  20  feet  high,  crocks  of  4  or  5 
gallons  capacity;  and  trees  21  to  30  feet  high,  crocks  of  5  or  6  gallons 
capacity.  For  trees  up  to  about  18  feet  in  height  one  crock  will  be 
needed  for  each  tent,  but  for  larger  trees  two  crocks  should  be  used, 
dividing  the  dosage  into  two  equal  parts.  Crocks  with  straight  sides 
can  be  used  with  more  cyanid  for  each  gallon  of  capacity  than  crocks 
which  narrow  at  the  top,  and  it  is  to  the  former  style  rather  than  to 
the  latter  that  the  preceding  statements  refer. 

The  foregoing  directions  should  enable  anyone  preparing  to  fumi- 
gate to  determine  the  actual  number  and  sizes  which  will  be  needed. 
It  is  always  advisable  to  have  several  extra  crocks  at  hand,  so  that 
delays  will  be  avoided  in  case  of  breakage. 

Crocks  of  more  than  2  gallons  capacity  can  not  be  readily  obtained 
as  a  rule  and  frequently  even  the  smaller  sizes  can  not  be  obtained 
of  local  dealers  in  sufficient  numbers  to  equip  a  large  outfit.  It  is 
important,  therefore,  that  orders  for  crocks  be  placed  as  soon  as 
possible  when  preparing  to  fumigate.  As  the  tops  or  covers  are  not 
needed,  dealers  should  take  this  into  consideration  in  quoting  prices. 
When  not  purchased  of  local  dealers  and  no  allowance  is  made  in  the 
price  on  account  of  the  covers  of  the  crocks,  instructions  should  be 
given  not  to  include  the  covers  in  the  shipment,  in  order  to  avoid 
unnecessary  freight  or  express  charges. 

[Cir.  ill] 


Convenient   bandies  for  the  crocks  can  be  made  ol  a  large  siz< 
wire.     If  properl)  arranged  the  ends  of  the  handle  will  be  held  in 
position  "ii  opposite  sides  <>f  the  crock,  otherwise  the)    ma}   cause 
considerable  anno)  ance. 

MISCELLANEOUS    REQUIREMENTS 

Of  tin*  numerous  articles  "I  minor  importance  which  Bometimes 
art"  not  easilj  obtained  and  should  therefore  be  arranged  for  as  earl) 
as  possible  are  rubber  gloves  and  glass  graduates.     Two  or  three 

pairs  of  rubber  gloves  should  I btained  For  a  large  outfit.     One 

pair  is  Deeded  for  the  one  who  measures  the  acid  and  generates  the 
gas,  and  one  pair  should  be  available  for  use  bj  the  helper  who 
empties  the  contents  of  the  crocks  after  fumigating.  The  third  pair 
should  be  on  hand  in  case  one  of  the  pairs  in  use  is  lost  or  destroyed 
hv  any  means.  Rubber  gloves  can  be  purchased  of  or  ordered 
through  electrical  supph  houses  or  electric-light  companies.  Black 
rubber  gloves  with  cloth  lining  are  preferable  to  the  red  rubber 
gloves  without  lining  which  are  sometimes  used.  The  latter  are  not 
easily  removed  from  the  hands,  especially  after  they  become  wet  on 
the  inside,  and  are  on  this  account  very  troublesome.  One  should 
avoid  gloves  which  are  so  thick  that  a  wel  glass  graduate  can  not  be 
easily  handled  when  wearing  them. 

A    glass  graduate   Of    16   ounces   capacity    is   needed    for  each   Outfit, 

and  if  not  obtainable  of  local  dealers  one  or  two  extra  one-  should 
be  always  on  hand.     They  can  be  purchased  through  local  druggists 

or  directly  of  wholesale  drug  houses.  It  is  important  that  the  num- 
bers on  the  graduate  be  plain  and  easily  readable. 

Torches  are  preferable  to  lanterns,  and  if  possible  three  or  four 
of  the  former  should  be  obtained. 

Balance-,  stoneware  pitcher-,  dippers,  water  buckets,  ropes,  pul- 
leys, and  other  article-  can  usually  be  obtained  of  local  merchant-. 

<  lll'.MM    u  - 

The  chemicals  required  in  fumigation  with  hydrocyanic-acid 
are  potassium  cyanid    K('\    and  sulphuric  acid  ill. so,  . 

POTASSIUM    CYANID 

The  cyanid  ordinarily  used  in  fumigating  citrus  tree-  is  put  up  in 
200-pound  cases  and  costs  between  21  and  23  cent-  a  pound  in  ton 
lots.  It  should  be  guaranteed  to  be  98  to  99  per  cent  pure.  In 
calculating  the  amount  of  cyanid  required,  a  tree  should  be  selected 

Which  represent  -  a-  Dearly  a-  can  he  e-t  imated  the  average  -i/.e  of  t  he 

trees  in  the  grove.  The  distance  over  the  top  can  be  obtained  l>\ 
the  tape  measure  in  the  same  manner  as  described  in  connection  with 
estimating  the  sizes  of  tents  required.  In  addition  to  this  measure- 
ment   the    circumference  of    the    tree   should    he  measured  with    the 


9  baa  i a  used  by  the  authors  for  this  i>uri*>-.- 

[Ctr.  ill] 


8 


tape  lino.  This  can  be  done  by  attaching  the  free  end  of  the  tape  to 
a  twig  and  passing  around  the  tree,  hanging  the  tape  on  the  outer 
twigs  as  it  is  unreeled.  If  the  grove  consists  of  two  sizes  of  trees,  as, 
for  example,  large  seedling  and  medium-sized  budded  trees,  an  aver- 
age specimen  of  both  kinds  should  be  measured.  The  amount  of 
cyanid  required  for  these  average  specimens  can  be  determined  from 
the  dosage  table  given  herein.  The  following  examples  illustrate  the 
method  of  using  the  table  after  the  distance  over  and  the  circum- 
ference of  the  tree  have  been  obtained. 


Example 

No. 

Distance 
over  tree. 

Circumfer- 
ence of  tree. 

Amount  of 

potassium 

cyanid 

required. 

1 
2 
3 
4 

Feel. 
2! 
38 
52 
66 

Feet. 

40 
53 

72 
79 

Ounces. 

9 

26 

58 

96 

The  amount  of  cyanid  in  ounces  having  been  obtained  for  the  aver- 
age tree  in  the  grove,  this  amount  is  multiplied  by  the  total  number  of 
trees  to  be  treated  and  divided  by  16  to  reduce  to  pounds.  It  is  advis- 
able to  obtain  from  5  to  10  per  cent  more  cyanid  than  the  amount  esti- 
mated, in  order  to  avoid  delays  in  case  of  underestimation.  The 
cyanid,  being  put  up  in  air-tight  tin  cases  inclosed  in  stout  wooden 
boxes,  may  be  stored  for  months  without  deterioration.  Excess 
cyanid  can  usually  be  disposed  of  without  difficulty. 


SI  I.l'lU'KIC    ACID. 


Sulphuric  acid  can  be  purchased  in  iron  drums  containing  about 
1 ,500  pounds  at  about  1  fV  cents  a  pound.  One  drum  of  acid  is  required 
for  about  4  cases  of  cyanid.  The  acid  should  be  guaranteed  66° 
Baume  or  93  percent  pure.  It  is  advisable  to  have  a  sample  tested 
with  an  acid  hydrometer,  an  inexpensive  instrument  which  can  be 
obtained  through  any  druggist.  Acid  should  not  be  stored  for  more 
than  two  or  three  weeks  in  the  drum.  Unless  it  is  to  be  used  at  once 
the  entire  contents  should  be  emptied  into  carboys,  the  mouths  of 
which  should  be  closed  with  wooden  plugs,  strips  of  burlap,  and  plaster 
of  Paris.  Empty  carboys  can  be  purchased  for  SI. 50  or  SI. 75  each, 
and  9  are  required  to  contain  the  contents  of  an  acid  drum.  Only 
carboys  in  good  condition  should  be  used,  since  the  container  is  made 
of  thin  glass  and  breaks  easily  if  the  bottom  of  the  wooden  case  becomes 
weakened  and  fails  to  support  the  contents.  Great  care  should  be 
used  in  handling  the  acid.  Probably  the  quickest  and  safest  way  of 
emptying  acid  from  the  large  drum  into  carboys  is  a  method  which 
has  been  used  on  several  occasions  by  the  authors.  The  drum  is 
mounted  on  two  heavy  planks  resting  on  the  ground  and  is  arranged 
so  that  it  can  be  rolled  forward  and  backward  easily.     At  one  end  of 

[Cir.  ill] 


the  planks  b  |»ii  aboul  3  feel  deep  is  dug.  Thia  Bhould  be  large  enough 
for  two  men  to  stand  in  and  place  the  emptj  carboj  in  position  and 
lift  it  out  when  filled.  A  large  mouthed  funnel  madeofsheel  lead  is 
placed  in  the  mouth  of  the  carboj  .  A  piece  of  casl  iron  piping  aboul 
6  or  8  inches  long  and  properly  threaded  is  a  convenience,  bul  not  a 
requirement.  This,  if  available,  is  Bcrewed  into  the  opening  in  the 
drum,  which  i--  arranged  so  that  the  acid  will  pour  into  the  funnel  lead- 
ing to  the  carboj.  A  piece  of  beavj  plank  or  other  suitable  lumber 
should  be  si  ronglj  spiked  across  the  ends  of  the  two  plank  supports  of 
the  drum  to  proven!  its  being  rolled  too  far  forward.  Whenever  there 
is  n  suitable  platform  available,  <>r  timber  is  available  for  making 
n  rough  one,  the  trouble  of  digging  the  pil  can  be  oh\  iated.     It  is  not 

/ 


10 

9 

8 

X 

N 

7 

X 

X 

6 

5 

5 

X 

X 

M 

/v 

fSi 

4 

X 

28-36 

9 

33-40 

13 

32-39 

is 

3 

37-45 
17 

25-30 

7 

30-37 
10^ 

37-46 
18 

2 

30-36 

io'i 

40-61 

25 

33-40 
13 

38-54 
20^2 

X 

1 

98-44 

17 

38-50 
19 

37-51 
19 

36-40 
14 '1 

Flo  i.-   Diagram  of  ngularly  set  grove  In  proceas  of  fumigation  with  «n  on tflt  of  four  ten tg    \    \ 

I  Merrill 

a«l\  isable  to  empty  drums  from  railroad  stations  or  packing-house  plat- 
forms, as  more  or  less  acid  is  usually  spilled.  No  .in,'  should  stand 
uear  the  carboy  when  the  acid  is  being  poured,  and  care  should  be  taken 
to  prevent  any  spattering  of  the  ami  from  reaching  the  face.  When 
handling  acid  it  is  always  well  t<>  have  water  at  hand  for  use  in  case 

of  incident.      With  proper  care  sulphuric  acid  can  he  handled  without 

danger  of  any  kind. 


DIAGRAMS    OP   GROVES,  AMD    DOSAGE    rABLES 

While  it  i^  not  always  necessary  that  diagrams  of  groves  be  made. 

it   is  always  advisable  as  a  matter  of  record  and  to  prevent   errors. 

Figures  2  and  :\  illustrate  methods  «.f  making  diagrams  when  trees 
rcir.  mi 


10 

are  set  in  the  square  and  in  the  alternate  system,  respectively.  The 
figures  in  the  squares  represent  the  records  of  the  trees  fumigated, 
the  two  upper  figures  separated  by  a  dash  representing  the  dimen- 
sions of  the  tented  tree  and  the  lower  figure  the  amount  of  cyanid 
given."  These  records  are  made  at  the  time  each  tree  is  fumigated. 
In  presenting  the  dosage  table  recommended  in  Bulletin  76  it  was 
stated  that  the  amounts  of  cyanid  could  be  increased  from  10  to  25 
per  cent  with  advantage  under  certain  conditions.  At  the  present 
time  the  authors  advise  for  general  use  a  table  (fig.  4)  representing 

M 


9 

V 

8 

7 

6 

W,     5 

X 

X 

4 

42-54 

24 

43-62 
29 

3 

39-47 
20 

40-49 
21 

X 

41-51 
23 

2 

42-50 
23 

47-60 
34 

40-47 

20 

43-48 
24 

■ 

32-38 

13 

42-50 
23 

i 

B 


D 


Fig.  3. — Diagram  of  grove  with  alternating  trees;  first  four  rows  in  process  of  fumigation  with  four  tents. 
three  sets  of  trees  fumigated,  the  tents  being  moved  from  south  to  north:  X,  X,  X,  trees  missing.  (From 
Morrill.) 

an  increase  of  25  per  cent  over  the  minimum  requirements  previously 
given  in  tabular  form.  This  seems  desirable,  owing  to  the  wide 
variations  in  the  weave  of  various  tenting  materials  and  to  the  fre- 
quency with  which  slight  winds  might  interfere  with  the  results. 


MISCELLANEOUS    SUGGESTIONS. 

With  the  gradual  extension  of  the  process  of  fumigation  in  the 
control  of  the  white  fly  in  Florida  and  other  citrus-growing  sections 
of  the  Gulf  coast,  the  value  of  a  citrus  grove  will   be  considerably 

"  The  amount  is  according  to  the  dosage  table  given  in  Bulletin  76  of  this  Bureau. 
page  68. 

[Cir.  Ill] 


I] 

affected  l>\  the  difficulties  in  Fumigation  presented  bj  excessive 
heighl  of  trees,  closeness  of  planting,  unevenness  "l  ground,  and  ol  her 
conditions.  The  systematic  treatment  <>l  groves  i"  overcome  these 
difficulties,  so  that  the  trees  ma}  !>■■  easil)  fumigated,  will  Qol  onl) 
be  of  value  in  this  respect,  but  will  constitute  a  good  cultural  practice. 
Trees  planted  too  closelj  for  fumigation  to  be  practicable  are  too 
close  for  besl  results  in  productiveness.  Limiting  the  I n •  i lt J •  t  <<(  trees 
l>\  pruning  not  only  lessens  the  expense  "f  fumigation,  but  reduces 
the  expense  of  picking  the  fruil  without  reducing  the  quantity. 


MM 

C/RCUM^ERENCE. 

Off* 

OV£S 

10,15 

20  25 

30,35 

4045 

50  52*5557* 

6062*65  67' 

70  72'75  77' 

8062'8587» 

«J 

,10 

12 

2    2 

2 

m 

3     3 
3*. 3' 

3 

3'  3' 

12' 
14    1 

1 

14 

16 

4     4 

4    4 

■X 

16. 

ie 

,  5 

5    5 

5     5 

18 

1 

10  15 

20  25 

30  35 

4045 

50  52'  55  57* 

60  62'6567' 

70  72*  75  77' 

8082' 85  87' 

X) 

20 

5' 

5-  5* 

5'   5' 

20 
22 
24  2 

22 

5«  6' 

6* 

6' 
6 

7 
9 

2 

24 

6'    7-' 

7- 

9- 

26 

9 

9    9' 

10    II 

26 

|28 

10 

II    II 

12    13 

13 

28 

10   15 

20  25 

30  35 

4045 

50,52*.  5557' 

60  62' 65  67' 

70  72'  75  77' 

80  82' 85  87' 

v> 

30 

12 

13 

13    14 

15 

30 
32 

34  3 
36 

12 

13 

14 

15    16 

18     19 

3 

36 

15 

15 

16    18 

19 

21    23 

22*23*25 

24!26*27 

17 

18 'l9 

21 

38 

,'9 

20  21 

23 

28 

38 

30  35 

4045 

50  52-5  5  57' 

60  62' 65 

67' 

3 

72' 

79 

77* 

•r 

82' 

85 

<?:" 

90 

| 

22  23 
23*26 

26  27  28 
28'30'3I 

iO 

31    32 

40. 

32 

33  35  36 

42 

44  4 
46 
46 

4  4 

28 

30  31  '33  35 

36   37  39  40 

42 

33  34*36  37 
35'37'38'39 

39  40  42  43 
42  4345  47 

4547  49 
48   50   51 

46 

53 

1 

404'. 

50  52'  55  57' 

60  62' 65  67' 

70  72'  75  77' 

80  82 

}6 

.50 

39.4!   43 

45  46  49   51 
47  49  51    53 
50   53   55   58 

53  55   57  58 
56-58-60'62 
60'62'64'66 

60 

50 

5  I 

,43  45 
46  48 

64  66 
68*70   73 

52 

54   5 
56. 
58 

58 

51 
53 

53   56   58  61 
=6   59  •      64 

63  66  68  71 

67' 70  72   75 

73  75  77  79 
78  80  82  84 

50  52 

60  62'  65  67' 

70  72'  75  77' 

80  82!  85  872 

;'0 

6 

60 
62 
64 
66 

60  63   65  68 
62  65  68  72 
66  69.72.76 

70  73   76   79 
75  78  80  83 
79.8265.89 
84  87  89  93 
87 '90 '93 '97 

82  85  88  91 
86  89  91.94 
92  95  98  101 

97IIOU04'l07 
IOI'I05'I09'!I3 

..: 
97 
04 
III 

i 

60 
62 

64  6 
66 

68 

69   73  76 

30 

73    77    80 

60  62'  65  67' 

70  72'  75  77' 

80  82' 85  87^ 

JO 

77  80  83  87 

90  94  98  102 

106  110  114  113 

:.= 

70 
72 

74,7 
76 

72 

80  83  86  90 

94  98  103  107 

III    115  119  123 

127 
133 
139 

7 

74 
76 

84 

s? 

90 

39 
94 

94 

93 

98 
102 

103 

107 

107 

112 

112 

117 

116 
121 

120 

i25 

124 

129 

128 
134 

Flo.  1      1 '  ,1 

In  preparing  for  the  fumigation  of  a  grove,  if  the  branches  inter 
lock  to  any  extent,  either  pruning  of  branches  or  transplanting  of 
alternate  trees  or  rows  of  tree-  i->  ad\  isable.  Deadwood  <>n  the  outer 
parts  of  the  trees  should  l>e  thoroughly  removed  in  all  cases  to  avoid 
the  tearing  <>f  tents.  Watershoots  should  be  thoroughly  removed 
at  the  same  time,  since  about  I  per  cent  of  the  white  fly  pupa'  present 
during  the  winter  months  survive  fumigation  and  the  resistance  of 
the  insects  <>n  watershool  leaves  is  much  greater  than  elsewhere  <>n 

the  t; 

[Cir.  lll| 


12 


UNIVERSITY  OF  FLORIDA 

nun  mi  in 

3  1262  09216  5579 


If  possible,  the  cultivating  and  fertilizing  of  groves  to  be  fumigated 
should  follow  fumigation.  It  is  much  more  difficult  to  handle  the 
fumigating  tents  on  newly  cultivated  ground,  and  the  dust  arising 
in  the  shifting  of  the  tents  is  sometimes  a  matter  of  considerable  dis- 
comfort to  the  men  engaged  in  the  work. 

Approved: 

W.  M.  Hays, 

Acting  Secretary  of  Agriculture. 

Washington,  D.  ('..  August  10,  1909. 

[Cir.lll] 

O 


